Add unit tests for pure utility functions in useMobileUpload

[kanweiwei]

web/src/hooks/useMobileUpload.ts contains several pure utility functions that are easily testable without any React rendering:

• formatFileSize() (line 83) — formats bytes to human-readable sizes
• validateFile() (line 96) — validates file size/type constraints
• generateFileId() (line 111) — generates unique IDs
• isFilePickerSupported() (line 122) — checks API support
• isIOSSafari() (line 129) — browser detection
• isMobileDevice() (line 141) — mobile detection
• getMimeTypeFromExtension() (line 217) — MIME type lookup

What to do:

1. Read web/src/hooks/useMobileUpload.ts and extract the pure functions (or export them)
2. Create web/src/hooks/__tests__/useMobileUpload.test.ts
3. Write tests for each function, covering edge cases:
   • formatFileSize(0), negative values, very large values
   • validateFile with oversized files, unsupported types
   • getMimeTypeFromExtension with unknown extensions
4. Run: pnpm -C web run test -- --run useMobileUpload

Skills needed: TypeScript, Vitest

Estimated time: 1-2 hours

[snakefood3232]

I'll extract and test those pure utility functions from useMobileUpload.ts like formatFileSize() and validateFile(). I'll create comprehensive Vitest unit tests covering edge cases for all seven functions. I can have a PR with the test suite ready in about an hour.

[snakefood3232]

I'll extract and test those pure utility functions from useMobileUpload.ts like formatFileSize() and validateFile(). I'll create comprehensive unit tests with Vitest covering all edge cases mentioned. I can have a PR with the test suite ready in about an hour—I frequently write TypeScript tests for React hooks in my projects.

[snakefood3232]

I'll extract and test those pure utility functions from useMobileUpload.ts. I'll create comprehensive unit tests with Vitest covering all edge cases like formatFileSize(0) and invalid file validation. Can have this PR ready in about an hour—I regularly write TypeScript test suites for production React codebases.